1. Field of the Invention
The present invention relates to an optical information recording medium, and more particularly, to an information recording medium that can be rapidly finalized, and a recording/reproducing apparatus and method using the same.
2. Related Art
Optical recording media (optical disks) are used in optical devices that record/reproduce data in a contact-less manner. Optical disks generally include compact disks (CD's) digital versatile disks (DVD's), high-definition video disks (HD-DVD's), blue-ray video disks (Blu-Ray) and other media used to digitally store data in a contact-less manner according to the information recording capacity. Some optical disks are writable or re-writable by a user to store data, video or audio. Examples of record/erase/read optical disks include a 650 MB CD-R, a CD-RW, a 4.7 GB DVD+R/RW, a DVD-RAM, and a DVD-R/RW. Examples of read-only disks include a 650 MB CD, a 4.7 GB DVD-ROM, HD-DVD and a Blu-Ray disk. Moreover, other technologies are under development to record data at higher densities and faster speeds using developmental optical media.
DVD-RAM and DVD-RW media generally have a recording data capacity of 4.7 GB, and are capable of having data recorded on, erased or reproduced there from. Specifically, each optical disk has grooves to guide an optical pick-up along tracks in a circumferential direction during a data recording operation. The grooves are formed during mastering of the disk, that is, when a stamper for a substrate is manufactured.
However, the greatest difference between a DVD-RAM and a DVD-RW is the recording area. In the DVD-RAM, data is recorded in both a groove area and a land area disposed between two adjacent groove areas. Also, for access based on a physical unit, a physical identifier (ID) area containing the address of each unit is formed as a pit series. In contrast, in the DVD-RW, data is recorded only in a groove area and no pits are formed. Instead, block addresses are formed in a land region as land pre-pits.
In addition, the DVD-RW has good recording/reproducing characteristics such as a superior jitter characteristic due to the depth and width of the groove. Advantageous jitter characteristics provide better jitter margins to allow superior flexibility with optical read/write devices that may produce a transport spin speed too high or too low for the media. The width and depth of the grooves in a DVD-RW are determined for excellent jitter characteristics without pits. An appropriate depth of the DVD-RW grooves is about 20-40 mm, which can be expressed as λ/12n, using the wavelength (λ) of a laser beam and the refractive index (n) of the disc. This groove depth of the DVD-RW is smaller than that of a DVD-RAM, which is expressed as λ/6n.
FIGS. 1A through 1D are graphs illustrating reproduction signals calculated according to the depth of the pit when a wavelength is 650 nm, an NA is 0.60, and a minimum mark length is 0.42 μm. In FIGS. 1A through 1D, a horizontal axis represents time in terms of ns, and a vertical axis shows normalized values of the reproduction signals. FIG. 1A illustrates a reproduction signal obtained when the depth of the pit is λ/3; FIG. 1B illustrates a reproduction signal obtained when the depth of the pit is λ/4; FIG. 1C illustrates a reproduction signal obtained when the depth of the pit is λ/6; and FIG. 1D illustrates a reproduction signal obtained when the depth of the pit is λ/12.
FIG. 2 shows the result when normalization is performed using the maximum value, that is, the signal from the depth of the DVD-RAM. Referring to FIG. 2, when the pits are formed below λ/12 (0.08λ), a reproduction signal of a 3T or 14T mark has a signal level corresponding to about 30% or less of the result given at the depth of λ/4 (0.25λ). Therefore, no reliable pit signals can be obtained from this signal. Consequently, the depth of the pit needs to be adjusted.
Since the pit and the groove in the DVD-RAM have a depth of approximately λ/6, a push-pull signal from the groove and the reproducing signal from the pit can be easily obtained. However, because the groove depth of a DVD-RW is much shallower, if the pits were the same depth as the groove, a push-pull signal from the pits would be difficult to obtain. As a result, a DVD-RW produced with grooves and pits having different depths would improve pit reproduction signal levels.
To address this problem, U.S. Pat. No. 5,501,926 discloses a technique of manufacturing two pits and grooves with different depths by the use of a special photoresist and an etching process. However, drawbacks to this technique may include complex manufacturing processes and high manufacturing costs.
U.S. Pat. No. 5,500,850 also discloses a process of manufacturing grooves with different depths. However a problem arises in that the paths of two laser beams have to be adjusted very precisely so as to form the grooves with different depths.
Likewise, an etching process can be utilized several times to define pits and grooves with different depths. That is, a dual-depth disk can be manufactured using an etching process. However, the manufacturing process is also complex and the production yield is low. As a result, production cost of the disk can be very high.
To overcome these drawbacks, a superior method of forming grooves and pits with different depths has been proposed by controlling a power of a laser beam as disclosed in Applicants' earlier work product, Korean Patent Publication Gazette No. 2001-0108961, and now issued as U.S. Pat. No. 6,906,994, the disclosure of which is incorporated by reference herein.
Nevertheless, there is still a need to rapidly finalize an optical disk manufactured as proposed.